Tension regulator



June 9, 1942. c. R. HANNA ETAL TENSIONfiEGULATOR Filed April 30, 1941 IINVENTORS C/mzon f #02074 (Illa xggan/ey 1% Mk/flg.

M 53 kmmukmkm Patented June 9, 1942 TENSION REGULATOR Clinton R. Hanna,Pittsburgh, and Stanley J.

Mikina, Wilkinsburg, Pa., assignors to Westinghouse Electric aManufacturing Company, East Pittsburgh, Pa., a corporation ofPennsylvania Application April 30, 1941, Serial No. 391,082

10 Claims.

This invention relates to regulators, and particularly to tensionregulators.

In the winding of coils of insulated wire such as are used indistribution transformers and the like, the coils are usually formed ofa rectangular or irregular shape on mandrels or the like having thepredetermined shape of the desired coil. The wire is wound on themandrel at the rate of several hundred feet per minute, being unwoundfrom a standard round supply reel that is restrained by a frictionbrake, to produce a tightly wound coil due to the wire tension requiredto overcome the friction of the reel brake.

Because of the irregular shape of the mandrel and the coil being wound,and the rapid winding rate, it is found that the wire supply reel issubjected to a harmonic acceleration that causes large variations in thewire tension. For example, as the mandrel turns, and assuming that themandrel is rectangular in shape, as the wire is wound on the fiat sideof the rectangle, there is a sudden increase in the wire speed as itapproaches the corner of the mandrel. The force for accelerating thewire reel is supplied by the wire as it is wound on the mandrel, withthe result that the wire is sometimes jammed between the turns on thereel by the excessive tension introduced, thereby causing damage to theinsulation of the wire and unduly stretching the wire. This condition isalso encountered in starting the winding operation, the tensionintroduced tending to jam the wire between the turns of wire on thesupply reel.

An object of this invention is to provide in a regulator for controllingthe tension of a wire extending between a winding mandrel and a supplyreel for compensating for any changes in tension encountered, and to socontrol the compensation as to maintain the tension substantiallyconstant.

A further object of this invention is to provide in a. regulator forcontrolling the tension of a wire as it is wound on a mandrel from areel for compensating for any changes in tension encountered to maintainthe tension substantially constant, and to provide for. so controllingthe compensation as to prevent over-compensation,

' and to maintain the tension substantially constant even when themandrel is at rest.

Other objects of this invention will become apparent from the followingdescription when taken in conjunction with the accompanying drawing, inwhich:

Figure 1 is a diagrammatic illustration of the apparatus and circuitsembodying the teachings of this invention;

Fig. 2 is a perspective view of a cam employed in a part of theapparatus embodying this inven- I tion; and

Fig. 3 is a graph, the curve of which illustrates characteristics of thegenerator field current obtained by employing this invention.

Referring to the drawing, and particularly Fig. 1 thereof, thisinvention is illustrated by reference to the winding of a wire ill on anirregularly-shaped mandrel I2 from a supply reel i4. The mandrel i2illustrated is of rectangular shape such as is employed in industry forthe winding of coils for distribution transformers or the like, and isdisposed to be driven at a predetermined speed by any suitable motor IS.The motor I6 comprises an armature winding I8 and a field winding 20which are connected to any suitable source of supply (not shown).

As illustrated, a motor 22 is provided for cooperating in controllingthe speed of the supply reel l4 and the tension of the wire l0 betweenthe reel l4 and the mandrel l2. The motor 22 comprises an armaturewinding 24 and a field winding 26, the field winding being separatelyexcited from any suitable source of power (not shown). The supply reelI4 is carried on the armature shaft 28 and is, therefore, responsive tothe speed of the motor 22.

A generator 30, comprising the armature winding 32 and the field winding34, is disposed for controlling the speed of the motor 22. Asillustrated, the armature winding 32 of the generator 30 is directlyconnected across the armature winding 24 of the motor 22 for impressinga voltage across the motor, depending upon the excitation of thegenerator 30.

As illustrated, one end of the field winding 34 is connected through aresistor 36 and a variable resistor 38 to one side of the source ofsupply (not shown), the other end of the field winding 34 beingconnected through the resistor 40 to the other side of the source ofsupply (not shown). An iron core reactor 42 is also connected across thefield winding 34 of the generator III for cooperating to control theexciting current therein, as will be explained more fully hereinafter.

In order to further control the exciting current in the field winding 34of the generator 30, provision is made for bucking and reversing theexciting current in the field winding 34 under predetermined conditions.Thls is effected by impressing a direct-current voltage across theresistor 40, the impressed voltage being of a polarity opposite to thepolarity of the voltage of the normal source of supply of the excitingcurrent (not shown). The voltage impressed across the resistor 48 issupplied in the present embodiment from any suitable source ofalternatingcurrent supply (not shown) through the transformer 44 and therectifying device 48, as illustrated.

In the particular embodiment illustrated, the variable resistor 88 isformed of a plurality of resistor sections which are graduated in valuesof resistance increasing from one end of the resistor toward the other.The graduated resistor 88 illustrated and described gives the regulatorof this invention predetermined characteristics, as will be explainedmore fully hereinafter.

In order to control the number and sequence of resistor sections of theresistor 38, which are to be connected in series circuit relation withthe generator field winding 34, a primary control device 48 is providedand disposed to be operated in a predetermined manner. The primarycontrol device 48 is formed of a plurality of elongated conducting leafspring members 58,

having one end of each member secured in fixed spaced relation to eachother and extending through suitable insulating means, such as the block52, so that their free ends are self-biased against a sloped stop 54 ofinsulating material. The contact members 58 carried on the free endswill be in spaced relation to each other when the free ends seat againstthe sloped stop 54. Each of the fixed ends of the stack of elongatedconducting members 58 is so connected by a conductor 58 to a differenttap of the resistor 38 that the conducting spring members 58 of thestack are progressively connected to progressive taps of the resistor38. An insulated driving member 88 is disposed to be actuated underpredetermined conditions to progressively actuate the spring members 58away from the sloped stop 54 to progressively shunt the resistorsections of the graduated resistor 38, beginning with the resistorsections of small value. Any suitable means for mounting the drivingmember 88 may be utilized, or, as illustrated, the driving member can becarried by the free ends of the leaf springs 82 which are secured attheir other ends to the insulating block 52 by any suitable means (notshown). The primary control device 48 referred to hereinbefore isdisclosed and claimed in the copending application of C. R. Hanna, eta1. Serial No. 203,876, filed April 23, 1938, and assigned to theassignee of this invention.

The driving member 88 of the primary control device 48 is disposed to beactuated in accord ance with the tension of the wire l8 between thesupply reel l4 and the winding mandrel I2. As illustrated, the wire I8is supplied to the mandrel l2 over an idler pulley 84, which is carriedin a substantially non-friction manner at the end of an arm 88 mountedfor pivotal movement. In practice, although only one arm 88 is shown,two of the arms 88 are provided, being disposed in spaced relation, theidler pulley 84 being carried in a ball bearing mounting (not shown) onthe shaft 88 disposed between the ends of the arms 88. The other ends ofthe arms 88 are fixedly mounted on a shaft 18 which extends between andthrough suitable brackets 12, only one of which is shown, the shaft 18being disposed to be rotated therein. The bracket 12 is mounted on abase plate I4, which can be supported in any suitable manner such as ona motor housing, or otherwise (not shown), the base member 14 alsocarrying elongated arms 18, I8 and 88 disposed in spaced relation toeach other. The arms 18 and 88 carry stop members 82 and 84,respectively, at their free ends disposed in the path of movement of thearm 88 for limiting the extent of movement thereof.

As illustrated, the movement of the arms 88 carrying the pulley 84 in aclockwise direction about their pivotal shaft 18 is restrained by atension spring 88 carried between the free end of the elongated arm 18and the pulley carrying arms 88. The spring 88 is positioned to give atoggle action, so that uniform tension is maintained in the wire I8 overthe entire range of the pulley travel. This is evident for as the arms88 rotate in a clockwise direction, the spring 88 stretches and thecenter line of the spring approaches the pivotal shaft 18 of the pulleycarrying arms 88 by just the amount suflicient to keep the wire tensionconstant. Changes in the tension desired to be controlled in the wire l8may be made simply by changing the spring 88 which restrains the pulleyarms 88. The toggle action referred to hereinbefore is unimpaired, ifthe free length of the spring is kept the same in all cases. However,where it is desired to adjust the tension of any individual spring, theadjustment may be made by means of the nut 88 and the bolt 88 whichsecures one end of the spring 88 to the free end of the arm 18 to changethe effective length of the spring 88.

A cam 82 is carried on the end of the shaft 18 for controlling themovement of the driving member 88 in accordance with a movement of thepulley carrying arms 88. As more clearly illustrated in Fig. 2, the cam82 is in the form of a ring member, with the slope of the cam surfaceprogressing from the small end to the large end of the cam as the cam isrotated in a clockwise direction. The ring cam 82 is carried on the endof the rotatable shaft 18 in any suitable manner, or, as illustrated, issecured by means of the bolt 84 to the end of a block 88, which issecured to the shaft 18 as by means of brazing, or otherwise (notshown). In practice, the elements of the apparatus described are soassociated that the end of the driving member 88 rides on the camsurface of the cam 82, and is directly responsive to a movement of thepulley carrying arms 88.

In operation, assuming that the wire I8 has been threaded over the idlerpulley 84 to the mandrel l2, and that the motor I8 is driving themandrel at some predetermined speed, a tension is developed in the wirel8 as it is being wound. This tension causes rotation of the pulley arms88 and their pivotal shaft I8 against the restraining force of thespring 88 to position the arms 88 at some intermediate position betweenthe stops 82 and 84. The rotation of the pulley arm 88 rotates the cam82 to force the driving member 88 against the elongated conductingmembers 58 of the primary control device 48 to control the number ofresistor sections of the resistor 88 in circuit with the exciting field84 of the generator 88 to control the voltage impressed across the motor22, and thereby control the speed of the reel l4.

As the mandrel I2 is driven to wind the wire l8 thereon, its irregularshape tries to change the tension of the wire l8. At the same time,

, because the wire is being removed from the supthat the speed of thereel I4 is constantly changing as the wire is unwound therefromregardless of the shape of the mandrel 12.

Forgetting for the time being the eifect of the irregular shape of themandrel l2 upon the tension of the wire I8, and assuming that thewinding of the mandrel has just started, the pulley arm 66 will be in aposition adjacent the stop 82, so that substantially all of the resistorsections of the graduated resistor 38 are in circuit with the fieldwinding 34 of the generator 38, and the exciting current therein is at aminimum for impressing a very low voltage across the motor 22 to drivethe reel l4 at a very slow speed.

As the wire is unwound from the reel I4, more tension is developed inthe wire III to effect a rotation of the pulley arms 66 in a clockwisedirection about their pivot 18, and progressively drive the contactmembers 56 into circuit closing position to progressively shunt theresistor sections of the graduated resistor 38 from series circuit withthe field winding 34. The progressive shunting of the resistor sectionsof the graduated resistor 38 eifectively increases the excitation of thegenerator 38 to increase the speed of the motor 22, and consequentlyincreases the speed of the reel H to maintain a constant tension on thewire [8 as the diameter of the supply of wire on the reel I4 diminishes.

With the wire l8 threaded over the pulley 64 between the supply reel l4and the mandrel I2, and before actual winding of the wire on the mandrelI2 is started, or while the mandrel is at rest, a negative torque isdeveloped in the motor 22 to maintain the tension in the wire l8substantially constant. This negative torque is developed by impressinga polarity across the resistor 40 which is opposite to the polarity ofthe voltage of the normal exciting current supplied to the field winding34 of the generator 30. The effect of the opposite polarity suppliedthrough the transformer 44 and the rectifying device 46 is to buck theexciting current in the field winding 34 and provide a negativegenerator field current.

The cooperative efiect of the bucking of the exciting current, and thevariation of the resistor sections of the graduated resistor 38 througha change in position of the pulley arm 86 is illustrated in Fig. 3 ofthe drawing, in which the curve 98 represents the generator fieldcurrent developed, starting with a full reel at rest and progressinguntil the reel is empty. As illustrated, because of the bucking of thenormal exciting current, a negative field current is actually developedto knock down the generator residual and insure a zero speed of themotor 22, as well as develop a negative motor torque for maintaining thetension of the wire In at a desired value, even at zero winding speed.As the resistor sections of the graduated resistor 38 are progressivelyvaried, beginning with the sections of small value, it is seen that theexciting current increases progressively in accordance with the amountof resistance shunted from series circuit with the field winding by theaction of the driving member 68 in response to a movement of the pulleyarms 66 in a clockwise direction. The graduated resistor thuscompensates for the varying regulator sensitivity as the diameter of thesupply of wire on the reel becomes smaller.

At the same time that the resistor sections of the graduated resistor 38are varied, it is seen that the iron core reactor 42 cooperates with theresistor 38 for influencing the exciting current in the field winding 34of the generator 38, and consequently affects the speed developed in themotor 22. If the change in the resistor sections of the graduatedresistor 38 is a large change, shunting out large sections of theresistor 38, it is found that the impedance of the iron core reactor 42is so great as to cause more of the current from the source of supply toimmediately flow in the generator field winding 34, giving anapproximate rate of change correction for a change in the position ofthe pulley arm 86. If, however, the change in the resistor sections ofthe graduated resistor 38 is to cut in large sections of the resistor38, the iron core reactor 42 functions to effect a discharge through thefield winding 34 to boost the normal exciting current and prevent aquick decay in the exciting current. The iron core reactor 42 thusfunctions to stabilize the system of this invention, giving a generatorexcitation proportional to the rate of change of the idler pulley armposition and compensating for system delays.

As the wire I8 is wound on the mandrel l2, the tension of the wire I, ofcourse, varies depending upon the position of the mandrel l2 as it isrotated by the motor I6. For example, as the wire is wound on the flatside of the rectangular-shaped mandrel 12, there is a sudden increase inthe wire speed as the mandrel is rotated and the wire approaches thecorner of the rectangle. The increase in the wire speed efiects anincrease in the tension of the wire being unwound from the reel I4, sothat to prevent damage to the turns of the wire on the reel M, or theturns of the wire being wound upon the mandrel l2, it is necessary toincrease the speed of the motor 22 to increase the speed of the supplyreel I4 to decrease the tension of the wire.

The increase in the tension of the wire l8 effects a rotation of thepulley arm 66 in a clockwise direction about its pivot 18 to operate thedriving member 68 to shunt more of the resistor sections of thegraduated resistor 38 from series with the field winding 34 of thegenerator 30, and if the increase in tension to be compensated is alarge increase, large sections of the resistor 38 will be immediatelyshunted from the circuit. The shunting of the resistor sections 38causes a larger current to flow in the field winding 34, and if thesections shunted are of large value, the reactor 42 cooperates, asexplained hereinbefore, to permit most of the current to flow throughthe field winding 34 for effecting an immediate increase in theexcitation of the generator 38. This immediate increase in theexcitation of the generator 38 effects an increase in the voltageimpressed across the motor 22 to immediately increase the speed of themotor 22, and consequently increase the speed of the reel l4 tocompensate for the increase in the tension of the wire ID as it passesthe corner of the rectangular mandrel l2.

Of course, the tension of the wire I8 is immediately decreased as themandrel I2 is rotated to wind the wire ID on its fiat side, so that thereel l4 tends to run faster than is necessary for maintaining thedesired tension in the wire ID. The decrease in the tension of the wireI!) permits the spring 86 to actuate the pulley arms 66 in acounter-clockwise direction about their pivot 18 to so move the cam 92as to permit the spring members 62 to bias the driving member 68 awayfrom the elongated conductor members 50 to cut in progressively smallersections of the graduated resistor 38 in circuit with the field winding34. The cutting in of the resistor sections of the graduated resistor 38decreases the exciting current in the field winding 34, but if theresistor sections cut in are of such large value as would normally tendto immediately effect a large decrease in the exciting current, the ironcore reactor 42 functions to prevent such immediate large decreases inthe exciting current as it discharges through the generator fieldwinding 34 to give a'substantially gradual decrease or decay in theexciting current. The decrease in the exciting current in the fieldwinding 34 eflects a decrease in the voltage impressed across thegenerator 22, and efifectively decreases the speed of the supply reel Hto maintain the tension substantially constant on the wire III as it isbeing wound on the mandrel i2.

With the regulator of this invention, it is evident that it is possibleto compensate for variations in the amount of wire on the supply reeland variations in the tension developed in the wire as it is being woundon a mandrel of irregular shape, as well as maintaining the tensionsubstantially constant even when the mandrel is at rest. The change inthe speed of the reel motor is effected immediately upon a change in thetension of the wire between the supply reel and the winding mandrel.Further, provision is made for obtaining a rate of change of correctionin the speed of the motor depending upon the rate of change of the idlerpulley arm position, thus compensating for system delays. The regulatingaction is quick and accurate, and because of the construction of thepulley arm assembly, which is usually a light, still frame of aluminumor other suitable light-weight metal or alloy, can follow the changes invelocity of the reel due to the irregular shape of the man drel on whichthe wire is being wound with a minimum of tension disturbance due to lowinertia forces.

We claim as our invention:

1. Apparatus for controlling the tension of a wire extending between awinding mandrel and a supply reel comprising, in combination, means fordriving the mandrel to wind the wire thereon, a motor cooperative tocontrol the speed of the reel and the tension of the wire, a pivotallymounted idler pulley associated with the wire and disposed for movementabout its pivot as the wire tension changes, an over-center spring soassociated with the pivotally mounted idler pulley as to rest-rainmovement of the pulley about its pivot as the tension of the wirebetween the mandrel and the reel increases, and means comprising avariable graduated resistor responsive to a movement of the idler pulleyabout its pivot for controlling the speed of the motor to control thespeed of the reel and the tension of the wire.

2. Apparatus for controlling the tension of a wire extending between awinding mandrel and a supply reel comprising, in combination, means fordriving the mandrel to wind the wire thereon, a motor cooperative tocontrol the speed of the reel and the tension of the wire, a pivotallymounted idler pulley associated with the wire and disposed for movementabout its pivot as the wire tension changes, an over-center spring soassociated' with the pivotally mounted idler pulley as to restrainmovement of the pulley about its pivot as the tension of the wirebetween the mandrel and the reel increases, and means including avariable graduated resistor and a reactor cooperative therewithresponsive to a movement of the idler pulley about its pivot and to therate of change of the motion of the pulley about its pivot to controlthe speed of the motor to control the speed of the reel and the tensionof the wire.

3. In a regulator for controlling the tension of a wire as it is woundon a mandrel from a reel, in combination, means for driving the mandrelto wind the wire thereon, a motor cooperative to control the speed ofthe reel and the tension of the wire, a generator having a field windingconnected to impress a voltage across the motor to develop a torque, avariable resistor having a plurality of resistor sections disposed to beconnected in circuit relation with the generator field winding tocontrol the excitation of the generator, means responsive to changes inthe tension of the wire for progressively, varying the number ofresistor sections connected in circuit with the generator field windingto control the energization of the field-winding and thereby control thetorque of the motor to maintain substantially constant tension on thewire as it is being wound, and means connected in circuit relation withthe generator field winding to buck the exciting current, thereby socontrolling the torque of the motor as to maintain the tension of thewire substantially constant when the mandrel is at rest.

4. In a regulator for controlling the tension of a wire as it is woundon a mandrel from a reel, in combination, means for driving the mandrelto wind the wire thereon, a motor cooperative to control the speed ofthe reel and the tension of the wire, a generator having a field windingconnected to impress a voltage across the motor to develop a torque, aresistor having a plurality of resistor sections disposed to beconnected in circuit relation with the generator field winding tocontrol the excitation of the generator, means disposed to be operatedto progressively vary the number of the resistor sections connected incircuit with the field winding, means responsive to changesin tension ofthe wire disposed to operate said resistor varying means to control theenergization of the generator field winding and thereby control thetorque of the motor to maintain substantially constant tension on thewire as it is being wound, and means connected in circuit relation withthe generator field winding to buck the exciting current, thereby socontrolling the torque of the motor as to maintain the tension of thewire substantially constant when the mandrel is at rest.

5. In a regulator for controlling the tension of a wire as it is woundon a mandrel from a reel, in combination, means for driving the mandrelto wind the wire thereon, a motor cooperative to control the speed ofthe reel and the tension of the wire, a generatorhaving a field windingconnected to impress a voltage across the motor to develop a torque, avariable resistor having a plurality of resistor sections disposed to beconnected in circuit relation with the generator field winding tocontrol the excitation of the generator, the resistor being graduatedwith the sections progressively increasing in resistance from one end tothe other, means responsive to changes in the tension of the wire forprogressively varying the number of resistor sections connected incircuit with the generator field winding to control the energization ofthe field winding and thereby control the torque of the motor tomaintain substantially constant tension on the wire as it is beingwound, the varying means progressively connecting smaller sections ofthe resistor in circuit with the generator field winding as the wire isremoved from the reel to maintain a sensitive control of the excitationof the generator field winding as the reel is unwound, and meansconnected in circuit relation with the generator field winding to buckthe exciting current, thereby so controlling the torque of the motor asto maintain the tension of the wire substantially constant when themandrel is at rest.

6. In a regulator for controlling the tension of a wire as it is woundon a mandrel from a reel, in combination, means for driving the mandrelto wind the wire thereon, a motor cooperative to control the speed ofthe reel and the tension of the wire, a generator having a field windingconnected to impress a voltage across the motor to develop a torque, aresistor having a plurality of resistor sections disposed to beconnected in circuit relation with the generator field winding tocontrol the excitation of the generator, the resistor being graduatedwith the sections progressively increasing in resistance from one end tothe other, means disposed to be operated to progressively vary thenumber of the resistor sections connected in circuit with the fieldwinding, means responsive to changes in the tension of the wire disposedto operate the resistor varying means to control the energization of thegenerator field winding and thereby control the torque of the motor tomaintain substantially constant tension on the wire as it is beingwound, the operation of the resistor varying means progressivelyconnecting smaller sections of the graduated resistor in circuit withthe generator field winding as the wire is removed from the reel tomaintain a sensitive control of the excitation of the generator fieldwinding as the reel is unwound, and means connected in circuit relationwith the generator field winding to buck the exciting current, therebyso controlling the torque of the motor as to maintain the tension of thewire substantially constant when the mandrel is at rest.

7. In a regulator for controlling the tension of a wire as it is woundon a mandrel from a reel, in combination, means for driving the mandrelto wind the wire thereon, a motor cooperative to control the speed ofthe reel and the tension of the wire, a generator having a field windingconnected to impress a voltage across the motor to develop a torque, avariable resistor having a plurality of resistor sections disposed to beconnected in circuit relation with the generator field winding tocontrol the excitation of the generator, means responsive to changes inthe tension of the wire for progressively varying the number of resistorsections connected in circuit with the generator field winding tocontrol the energization of the field winding and thereby control thetorque of the motor, means comprising a reactor connected across thegenerator field winding for cooperating with the resistor as thesections connected in circuit are varied to so control the torque of themotor as to maintain substantially constant tension on the wire as it isbeing wound, and means connected in circuit relation with the generatorfield winding to buck the exciting current, thereby so controlling thetorque of the mo tor as to maintain the tension of the wiresubstantially constant when the mandrel is at rest.

8. In a regulator for controlling the tension of a wire as it is woundon a mandrel from a reel,

in combination, means for driving the mandrel to wind the wire thereon,a motor cooperative to control the speed of the reel and the tension ofthe wire, a generator having a field winding connected to impress avoltage across the motor to develop a torque, a resistor having aplurality of resistor sections disposed to be connected in circuitrelation with the generator field winding to control the excitation ofthe generator, means disposed to be operated to progressively vary thenumber of the resistor sections connected in circuit with the fieldwinding, means responsive to changes in tension of the wire disposed tooperate said resistor varying means to control the energization of thegenerator field winding and thereby control the torque of the motor, areactor connected across the generator field winding, the reactor beingcooperative as the resistor sections connected in circuit with thegenerator field winding are varied to give a sensitive control of theexcitation of the generator field winding and consequently the torque ofthe motor to maintain a substantially constant tension on the wire as itis being wound, and means connected in circuit relation with thegenerator field winding to buck the exciting current, thereby socontrolling the torque of the motor as to maintain a substantiallyconstant tension on the wire when the mandrel is at rest.

9. In a regulator for controlling the tension of a wire as it is woundon a mandrel from a reel, in combination, means for driving the mandrelto wind the wire thereon, a motor cooperative to control the speed ofthe reel and the tension of the wire, a generator having a field windingconnected to impress a voltage across the motor to develop a torque, avariable resistor having a plurality of resistor sections disposed to beconnected in circuit relation with the generator field winding tocontrol the excitation of the generator, the resistor being graduatedwith the sections progressively increasing in resistance from one end tothe other, means responsive to changes in the tension of the wire forprogressively varying the number 01' resistor sections connected incircuit with the generator field winding to control the energization ofthe field winding and thereby control the torque of the motor tomaintain substantially constant tension on the wire as it is beingwound, the varying means progressively connecting smaller sections ofthe resistor in circuit with the generator field winding as the wire isremoved from the reel, a reactor connected across the generator fieldwinding, the reactor cooperating with the resistor as the sectionsconnected in circuit are varied to so control the excitation of thegenerator field winding as to maintain a sensitive control of the torqueof the motor and thereby maintain a substantially constant tension onthe wire as it is being wound, and means connected in circuit relationwith the generator field winding to buck the exciting current, therebyso controlling the torque of the motor as to maintain the tension of thewire substantially constant when the mandrel is at rest.

10. Apparatus for controlling the tension of a wire extending between amandrel and a supply reel comprising, in combination, means for drivingthe mandrel to wind the wire thereon, a motor cooperative to control thespeed of the reel and the tension of the wire, a pivotally mounted idlerpulley associated with the wire and disposed for movement about itspivot as the wire tension changes, an overcenter spring so assomountedidler pulley disposed for translating the pivotal movement or the pulleyabout its pivot to a straight line movement to actuate the contactmembers progressively.

CLINTON R. HANNA. STANLEY J MIKINA.

